Cyclic drum printer

ABSTRACT

High quality non-impact printing based on transfer of images from a revolving font drum to a page blank carried by a receptor drum rotating with the same surface velocity as the font drum, but precessing with respect to the former, the images being developed upon transfer of a full page of information to the blank. Alternatively, the receptor drum can have an imagereceiving surface for intermediate storage of images and subsequent transfer of these images to a page blank for visual development or subsequent visual development and transfer of the visible images to a page blank.

United States Patent 91 Markakis CYCLIC DRUM PRINTER [75] Inventor: Michael J. Mnrkakis, Palo Alto,

Calif.

[73]' Assignee: SCM Corporation, New York, NY. [22] Filed: Sept. 18, 1972. [21] Appl. No.: 290,050

[52] US. Cl. 95/45, 340/378 UNITED STATES PATENTS 3,262,379 7/1966 Bauer "95/45 [in 3,741,086 June 26, 1973 Primary Examiner-John M. Horan Attorney-Armand G. Guibert et a].

[57] ABSTRACT High quality non-impact printing based on transfer of images from a revolving font drum to a page blank carried by a receptor drum rotating with the same surface velocity as the font drum, but processing with respect to the former, the images being developed upon transfer of a full page of information to the blank. Alternatively, the receptor drum can have an image-receiving surface for intermediate storage of images and subsequent transfer of these images to a page blank for visual development or subsequent visual development and transfer of the visible images to a page blank.

18 Claims, 2 Drawing Figures PAIENTEDwuzsnszs 3 741 086 sum 1 nr 2 1 CYCLIC DRUM PRINTER BACKGROUND OF THE INVENTION l. Field of the Invention The present invention relates to printing, and more particularly to apparatus for providing high quality printing using a nonimpact technique. Imaging operations upon a blank sheet of paper are carried out in successive cycles along a fixed path with characters at sequential printing stations being selectively imaged upon the sheet-at different lines in each cycle, the blank being advanced one line during each successive cycle art, such as U. S. Pat. No. 2,919,967, has shown systems having high speed drums moving past relatively slow speed paper with the result that the copy does not achieve maximum'quality. The apparatusaccording to the invention differs from such previous methods or apparatus in that the relative velocity of font and paper is zero in the area of print, thus producing no smear.

BRIEF SUMMARY OF THE INVENTION A principal object of the invention is to provide a page reproduction system having a number of reproduction stations, each station containing at least one discrete character generator, the character generators defining a curved surface and being spaced at equal intervals along the surface, together with a curved member record medium of particular length adjacent the surface, drive means for substantially equal velocity movement of the curved member and the surface in a series of cycles, the drive means precessing the record medium through a distance equal to one interval during each cycle, means forming images on the record mediumin response toselective operation of the character generators during any cycle, and means for developing the images after a number of cycles sufficientto' have presented each character generator over the length of the record medium.

A further object of the invention is to provide apparatus for imaging a large amount of information in successive stages on a blank sheet of paper, the fullyimaged page being subsequently developed.

Yet another object of the invention is to provide page printing apparatus for imaging in successive stages different and/oroverlapping areas on any sizeblank page, the fully-imaged page being subsequently developed.

A still further object of the invention is to provide a multi-stage printing mechanism having a rotatively mounted drum, which carries a blank page in successive cycles along a closed path past a plurality of printing stations, successive'lines of the blank page .being presented'to successive ones of the printing stations in each cycle, and the blank page being precessedone line during each cycle.

i.e., the number of characters BRIEF DESCRIPTION OF THE DRAWING FIG. 1 shows the geometricrelationship between the two drums, transfer timing, and paper feed and release according to the invention with portions cut away for the purpose of showing as many elements as possible; and

FIG. 2 shows a combined block diagram and pictorial of an electronic system that will work with the disclosed cyclic printer capable of reproducing all of the alphabetical symbols, as well as the decimal digits, blanks, and other selected and desired characters, such as 0, etc.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1, thereis disclosed a cyclic drum printer capable of reproducing a page of information by imaging any one of the characters on a multiplicity of character fonts 6 at desired locations on a sheet of dielectric paper 7. Printer 60 is arranged to print, line-by-line, any of 96 characters 6b on each of fonts 6, the characters being arranged in parallel rows 6a, for example. The information may be a computer output taking the form of a 7 bit binary code using 96 of the 128 available combinations, each representative of a different one of the characters 6b on fonts 6. It is to be understood that this arrangement is merely illustrative of the invention, and that, if desired, one may use a greater or smaller number of fonts 6 in each row 6a and characters 6b.

The reproduction elements of cyclic drum printer 60 consist of two separate drums (refer to FIG. 1): a font drum 3 which has a number of columnar characters on fonts 6 presented sequentially to a receptor drum 1. The characters on fonts 6 may be alphabetic, numeric, and special symbols suchas periods, commas, mathematical symbols, etc. Arrangement of characters 6b on the fonts 6 across the rows 6a is singular in kind all A's, all Bs, etc. Accordingly,,each character font 6 of drum 3 includes 96 distinct elements 6b in columnar alignment; hence, font drum 3 has a circumferenceof 96 units of length. If the distance along each unit is onesixteenth inch, corresp onding to the standard line spac a complete revolution every 100 milliseconds, to avoid need for precision balancing, although the printer could be operated at much higher speeds if desired.

Drum 1 supports the sheet of d electric paper 7 having a multiplicity of lines 7a on which selected charac- The foregoing, and otherobjects, features .and advanment of the invention,,as illustrated in the accompanying drawing. v

ters from each font .6 will be applied. Each sheet of paper 7 may have a capacity up to 84- lines 7a (legal size paper). Receptor drum 1 may be located such that there is a slight separation between its surface and that of drum 3 (see FIG. 2) and is arranged by means of gearing to run in a direction such that the relative surface velocity between the two drums is zero. Di meters and gears are chosen to cause the surface of drum 1 to advance one line space (one-sixteenth inch) per reyolution relative to the surface of'drum 3. Thus, receptor drum 1 has, in this example, a circumference of units .of length, of 15 5/6 inches. A gear 4 having 96 teeth is attached to .drum 3 and an .engaginggetlrfi ;hav-

the other gear, thereby rotating both drums at the same time. It can be shown that each unit of length on drum 3 will be placed opposite to or, as will be seen, in contact with each unit of identical length on drum 1 in 95 revolutions of drum 3, according to the following relation:

where N number of teeth and R number of revolutions. During one complete revolution of drum 3, characters of fonts 6 are available sequentially at corresponding positions in 84 lines 7a on paper 7, and are imaged as required. To exemplify, during the first revolution, on line 1 of paper 17 there would be imaged the As in that line of the text, on line 2, the Bs in this next line of the text; on line 3, all the Cs in this subsequent line of text, etc. Since there is a difference in circumference between drum 3 and drum 1, then at the end of the first revolution of drum 3 line 1 would be presented with the 96th character of fonts 6; and during the second revolution of drum 3: line 2, all the A's; line 3, all Bs, etc. Thus, after 95 revolutions of drum 3 (96 complete'revolutions of drum 1), any of the 96 characters 6b could have been imaged in all 80 positions of each line 7a, and'thus on the entire page '7. It should be noted that imaging of more than one character 6b within a given position on line 7a can be accomplished with this system, superposition of symbols permitting use of diacritical marks; underscoring, etc.

As previously noted, it takes 100 milliseconds for every revolution of font drum 3. Since there are 96 characters, movement of drum 3 from one character to the next takes 1-040 usec. In that 1040v usec. the system must readin a reference character, read in the first columnar character to be imaged, compare the two characters, clock out a comparison to a buffer shift register,

I and repeat the'comparison for each of the following columnar characters until all 80 have been compared.

Then, the comparison data can be shifted into another register in drum 3 for control of character imaging onto paper 7 on 'drum 1, asdescribed below. It should be noted at this time that character comparison and shifting occur at electronic speeds during the time when gap 60 between successive characters 6b of each font 6 is adjacent to paper 7 on drum 1.

-' On receptor druml there must be a means of paper feed and paper release 12, release occurring only when the complete page has'been imaged. Such a paper feed and release mechanism 12 could be similar to one shown in US. Pat. No. 3,213,786, FIG. 5. Each blank page is retained on a platen (such as drum 1, for instance) by a pair of similar, but reversed, wire clips havinga curved intermediate'portion which conforms to the curvature of drum 1'. The paper,7 is fed and released in the well-known fashion demonstrated in the above-mentioned patent. Release of the paper 7 is done after a complete page is imaged and the page is then sent to a development stage, not shown, but which can be similar-to thedevelopment units in U. S. Pat. Nos. 3,345,925 and 3,343,450.

In the imaging process now to be described, a selected font 6 of font drum 3 will have a high voltage placed upon it at the instant when transfer of a particular character 6b is to be made. In this kind ofarrangemerit, the font 6 in one-column must be isolated from those in adjacent columns so that there will be selectability as to thefont 6 where transfer is to be made.

When a font 6 is selected by having a high voltage applied to it momentarily, a contiguous area of the corresponding column on dielectric paper 7 held on drum 1 will be charged because of'the capacity of dielectric paper 7 and conductivity of drum 1, which may be connected to a low or ground reference voltage at 47. Note that the arrangement described could be reversed, the high voltage being placed on sections of drum 1 and low voltage on a continuous drum 3, if desired.

As for dielectric paper 7, it must be conductive on the side in contact with drum 1 and have a-thin dielectric coating (not shown), preferably in contact with drum 3 (or closely spaced thereto) for acceptance of imaging charges. The paper may be similar to coated paper Type 563 made by the Plastic Coatings Corp., Holyoke, Massachusetts and Forest paper, Type 566, supplied by Varian Corp., Palo Alto, California. On such paper, the best reproducibility is found with a voltage difference of about 700 volts to 800 volts when using liquid toners such as disclosed in U. S. Pat. Nos.

3,343,450 and 3,345,925, this combination giving a satisfactory dark or black composition for the symbols on the paper. I

On the other hand, as an alternative structure, there may be a resilient layer 2 on receptor drum 1 between dielectric paper 7 and the surface 1a of drum 1. The layer 2 must also be conductive and of a thickness such that the surface 7b of paper 7 makes a light contact with the'tops of the characters 6b on fonts 6, as shown in FIG. 1.

Once paper 7 is fed and lined up on receptor drum 1, imaging of characters 6a can be performed. For this purpose, as mentioned earlier, a voltage difference is connected across drum 3 and drum 1, in accordance witha high'voltage system containing a high voltage supply (not shown), together witha shift register and high voltage drivers (also not shown in FIG. 1 The latter two elements are preferably'located in and rotate with drum 3 to reduce the required number of slip rings 49,50. Such electronic-elements are well known in the art. Applicable sll'lft registers are'shown in"MOS/LSI from Texas Instruments Bulletin C8126 published by Texas Instruments Corp., October 1970. The high voltage drivers can be simple switching transistors such as, say, the 2N5015 of the NPN type connected in common emitter configuration with 800 volts applied to collector load resistors. Drum 1 and fonts 6 of drum 3 can be connected to respective ends of the resistors, and the transistor bases connected to appropriate parallel outputs of the shift register. The ground reference 47 on receptor drum 1 can remain constant, whereas the high voltage applied to selected fonts 6 of drum 3 must be switched on and off. As seen in FIG. 1, the current path for voltage system 8 is through font drum 3, to the selected character fonts 6', to the, surface 7b of paper 7, then through the paper capacitance to layer 2 (i.e., to drum 1) where a return path connection 48 is provided back to high voltage system -8. l

' Control of switching the high voltage on and off is done by electronic elements which digest input information and allow imaging to be accomplished in accord with that input information. Refer now to FIG. 2, which shows how selective transfer of information is accomplished. Print command signal 43 originates with the operator when, say, a computer output is to be printed. The location of markers 44 and 45, and the drive interconnection of drums l and 3, are such that a paper edge signal 42 and any one of a number of font position input signals 40 occur substantially at the same time. This is done so that imaging will not be started at midposition on any character ro'w 7a. Note further that this arrangement will also allow printing to start at any character position of fonts 6. There is a limitation here, of course, that on initial turn-on of the machine, the printing cannot start until there is a sensing of a font start index marker 46 as will be discussed subsequently.

Print command 43 feeds an input signal to quantizer 10 which synchronizes all signals. This output of quantizer 10 sets print page flip-flop 11. Set output 11a of print page flip-flop 11 is an input to start print gate 14, along with signal 13a from an amplifier/Schmidt trigger 13. Simultaneous concurrence of the two signals, 11a and 13a, will give an output 14a, which sets a print latch (or flip-flop) 15 to allow imaging of the selected character 6a as will be shown and discussed below. Output 140 starts a divide-by-96 counter 12, which is at count zero at the beginning of every print operation. An output signal 12a is obtained when divide-by-96 counter 12 reaches the value 96, terminating further imaging of characters 6b.

A font position input signal 40 is developed when each character font marker 45 is in proximity with font position input generator 40a. The function of font position input signal 40 will be discussed below. Each character font marker 45 is aligned with the angular position of a particular character row 6a.

The manner of sequentially selecting the proper character font 6 at the particular character row 6a desired, involves the use of digital electronics techniques, such as magnetic, optical, etc. controls. This is accomplished in my embodiments when a marker 44 comes in proximity with the paper edge input generator 42a. Paper edge marker 44 is set on drum 1 in such a location as to allow a margin at the top of paper 7 before imaging the first line'7b. Paper edge input generator 42a generates the above-mentioned paper edge signal 42 which goes to amplifier/Schmidt trigger 13 to create a fast rise/fall pulse 13a of appropriate amplitude. f

' A 'font start signal 41 is produced by a font start index generator 41a upon sensing a marker 46 which establishes the beginning position of font drum 3. Signal.41 is generated just prior to A row 6a. Font start" signal 41 is sent to an amplifier/Schmidt trigger 16,

- functions of which is the same as trigger 13 described previously. Output signal 16a of trigger 16 is then fed to a quantizer 17, which synchronizes all signals with the system clock 39 in the same fashion as does quantizer 10. Output signal 17a from quantizer 17 sets a binary font counter 20 to zero. Thus, when font position input signal 40 occurs through trigger 18, as timed by quantizer l9, font counter 20 starts to count beginning at zero and ending with 96. Each count is sent. to a reference character translator 21 by seven output lines 20a from font counter 20. Reference character transla- 1 tor 21 is needed when the code used for the date in main memory 29 is not the same as in font counter 20. Each count from font counter 20 is translated into one of the 96 reference characters by reference character translator 21, the output of which is sent to a character comparator 30. At this point, the reference character generated by font position input signal 40 can be compared with memory characters shifted to character comparator 30.

Main memory 29 holds an entire page of information to be imaged. A page can contain 84 lines having character positions per line with the possibility of any one of 96 different characters being in a given position. For my purposes, main memory 29 will be preferably a dynamic circulating memory. Memory information is obtained through various networks of input data fed in parallel, say, to a memory gating system 28 working synchronously with a memory control system 23. The inputs to this system 23 are a system clock 39, the font position input signal 40, and an address counter 22. The concurrence of the output signal 23a from memory control 23 and system clock 39 allows memory clock 24 to start running and feed a signal 24a to step main memory 29, character by character and line by line until the entire page has been scanned. In order to compare the correct line at the proper time, address counter 22 therefore acts as a control for main memory scanning. Address counter 22 will allow only the proper line from memory 29 to be compared in character comparator 30.

in order to compare all 84 lines of a page, a signal from character comparator 30 is sent to output clocking and control 27. Output clocking and control 27 is operated jointly by address counter 22, system clock 39, character comparator 30, and the output signal 15a from print latch 15, assumed to be present at this time. Because the system can compare 84 lines of a page, a line counter 26 is started by a signal 27a from output clocking and control 27. Of course, before the signal 27a from output clocking and control 27 is presented to the line counter 26, this last is set to a count of zero by the gating control 25 for signals 40a and 15a. Another of the functions of output clocking and control 27 is to allow only the proper number of character comparisons from comparator 30 to be used for imaging of each line. A comparison storage buffer 31 receives inputinformation from character comparator 30 serially, one bit as each memory character is compared tronic elements discussed previously by means of brushes and slip rings indicated symbolically (FIG. 2) at 49 and 50. High voltage power receiver 35 is activated by a signal coming from high voltage power control 33. Receiver 35, in turn, sends an output, but only after shift register 37 has received all 80 bits of information through data receiver 36 as supplied by output driver 34. Shift register 37 is, in effect, a serial-to parallel converter. It receives information serially and supplies it in parallel so that information for one line can be presented selectively to high voltage drivers 38. Once information in shift register 37 has been loaded serially, the output of shift register 37 and high voltage power receiver 35 will then be presented to high voltage drivers 38, comprised of 80 separate drivers, each representing a particular position within the writing line. Each driver 38 is connected by one of the leads 51 to a corresponding one of the fonts 6. Therefore, 80 character positions'of line 7a could be imaged at one time, should the same character be present in all positions. Each of the high voltage drivers 38 will be activated during the imaging of one character 6b starting with paper 7 near the top of the character and ending near its bottom, as drums 3 and 1 rotate.

It should be noted that the system must be able to successfully image all 84 lines of a page, using any and all 96 characters 6. Therefore, as discussed above, there will be 96 revolutions of the drum 1, each revolution accompanied with a complete count by line counter 26. Note that line counter 26 will reset print latch 15 only at the time it has completely counted through 84 lines. Once print latch 15 has been reset, printing of any further lines will be prevented until print edge input generator 42a again senses marker 44 at which time print latch 15 is set once more and line counter 26 will start counting anew. This process will repeat 96 times, but thereafter divide-by-96 counter 12 will give an overflow signal 12a to reset the Full-page latch 11, causing the level 11a to disappear and thus disable the start print gate 14 such that the paper edge input signal 13a will be ineffective, thereby ending the imaging operation.

The invention is not confined to the configuration described as the preferred embodiment. Alternate configurations or modifications to the imaging apparatus and system of producing copies may be employed. Such modifications are, say, applying well-known electrostatigraphic techniques which can use a wet or dry toner. For instance, electrostatic charge patterns on drum 3 could be deposited directly upon a dielectric material forming the surface of drum 1. Then the charge pattern could be either toned and the toned image transferred to bond paper; or the-electrostatic charge pattern could be transferred to a 'copy'paper for later toning, as is known. Another possible modification would be the use of an optical imaging apparatus for drum 3, cooperating with a photoconductive element on drum 1. An electrostatic charge layer deposited on drum 1 would be selectively illuminated in that case through a transparency on drum-3, containingtain specific terms of languages herein, it is to be understood that the present disclosure is illustrative rather than restrictive and that certain changes and modifications, including others than those herein-described, may be made without departing from the spirit or scope of the claims appended hereto. What is claimed is:

1. In a page reproduction system having aplurality of reproduction stations, each said station containing at least one discrete character generator, said character generators defining a curved surface and being placed at equal intervals along saidsurface, the combination of a curved member supporting a record medium of particular length adjacent said surface, drive means for equal velocity movement of said member and said surface in a series of cycles, said drive means precessing said record medium through a distance equal to one of said intervals during each said cycle,

means forming images on the record medium in response to selective operation of said character generators during any of the cycles, and

means for obtaining visible copies of said images after a number of cycles sufficient to have presented all characters in a station to each said interval of the particular length of the record medium.

2. A page reproduction system as defined in claim 1, wherein said record member is a page blank.

3. A page reproduction system as defined in claim 2, wherein said page blank comprises an insulating layer on a conductive backing.

4. A page reproduction system as defined in claim 3, wherein saidinsulating layer is mounted on a paper treated with a conductive material.

5. A page reproduction system as defined in claim 1, further including a resilient, conductive layer intermediate said supporting curved member and said record medium.

6. A page reproduction system as defined in claim 5, wherein said record member is a page blank comprising an insulating layer on a conductive backing.

7. A page reproduction system as defined in claim 6, wherein said insulating layer is mounted on a paper treated with a conductive material.

8. A page reproduction system as defined in claim 1, wherein said character generators comprise opaque symbols in columnar arrangement on the transparent surface of a first cylindrical drum, said curved member is a second cylindrical drum having as said record medium a photoconductive element on the periphery thereof andbeing axially spaced from said first drum, said means forming images comprise a source of electrostatic charges for forming a uniform charge layer on the photoconductive element and a plurality of light sources, each cooperating with a respective column of said symbols and selectively operable to illuminate desired ones of said symbols, including blanks, in each saidcolumn, and said means for forming visible images include. toning and transfer means.

9. A page reproduction system as defined in claim 1, further including a high voltage source, and wherein said plurality of reproduction stations comprises font wheels fixed to a common axis for simultaneous rotation, each font wheel being separately energizable by said high voltage source at selected intervals in said rotation.

10. A page reproduction system as defined in claim 9, wherein said record member is a page blank.

11. A page reproduction system as defined in claim 10, wherein said page blank comprises an insulating layer on a conductive backing.

12. A page reproduction system as defined in claim 11, wherein said insulating layer is mounted on a paper treated with a conductive material.

13. A page reproduction system as'defined in claim 9, further including a resilient, conductive layer intermediate said supporting curved member and said record medium.

14. A page reproduction system as defined in claim 13, wherein said record member is a page blank comprising an insulating layer on a conductive backing.

15. A page reproduction system as defined in claim 14, wherein said insulating layer is mounted on a paper treated with a conductive material.

16. A page reproduction system as defined in claim 7 9, wherein said curved member is a cylindrical drum transferred to said paper sheet and further including means for toning said imaged paper and means for fixing the toned image on said paper.

18. A page reproduction system as defined in claim 16, further including means for toning the images formed on the drum, means transferring toned images from the drum to said paper sheets, and means for fixing the toned image transferred to said paper.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 741,086 Dated June 26, 1973 Inventor(s) Michael J. Markakis It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Col. 9, line 7, change "comprise" to comprises line 8, delete "sheets" Cole 10, line 1, delete "sheets" line 7, delete "sheets" Add the following claims:

19, A page reproduction system as defined in claim 9, wherein said curved member is a cylindrical drum having as said record medium a dielectric material on the surface thereof, said means for forming visible copies of the images comprises paper fed past said dielectric material and further including means providing resilient contact between the dielectric material and said font wheels.

20., A page reproduction system as defined in claim 19, wherein said resilient contact means comprises a resilient conductive layer intermediate said dielectric material and said drum.

21 A page reproduction system as defined in claim 20, wherein charge images formed on said drum are transferred to said paper and further including means for toning said imaged paper and means for fixing the toned image on said paper.

22. A page reproduction system as defined in claim 20, further including means for toning the images formed on the drum, means transferring toned images from the drum to said paper, and means for fixing the toned image transferred to said papero Signed and Scaled this twentieth D of April1976 [SEAL] Arrest:

RUTH C. MASON C. MARSHALL DANN Arresting Officer (rmunissium'r nflarents and Trademarks UNITED STATES PATENT UFFICE CRTIFECATE 0F CORRECTION Patent No. 3,741,086 Dated June 26, 1973 Inventor(s) Michael J. Markakis It is certified that error appears in the aboveidentified patent and that said Letters Patent are hereby corrected as shown below:

Col. 9, line 7, change "comprise" to comprises line 8, delete "sheets" Cole 10, line 1, delete "sheets" line 7, delete "sheets" Add the following claims:

190 A page reproduction system as defined in claim 9, wherein said curved member is a cylindrical drum having as said record medium a dielectric material on the surface thereof, said means for forming visible copies of the images comprises paper fed past said dielectric material and further including means providing resilient contact between the dielectric material and said font wheels.

200 A page reproduction system as defined in claim 19, wherein said resilient contact means comprises a resilient conductive layer intermediate said dielectric material and said drum,

21., A page reproduction system as defined in claim 20, wherein charge images formed on said drum are transferred to said paper and further including means for toning said imaged paper and means for fixing the toned image on said paper,

22. A page reproduction system as defined in claim 20, further including means for toning the images formed on the drum, means transferring toned images from the drum to said paper, and means for fixing the toned image transferred to said papero Signed and Scaled this twentieth Day f April1976 [SEAL] A ttesr:

RUTH C. MASON C. MARSHALL DANN Arresting ()jjlcer ('mnmissimwr uflarents and Trademarks 

1. In a page reproduction system having a plurality of reproduction stations, each said station containing at least one discrete character generator, said character generators defining a curved surface and being placed at equal intervals along said surface, the combination of a curved member supporting a record medium of particular length adjacent said surface, drive means for equal velocity movement of said member and said surface in a series of cycles, said drive means precessing said record medium through a distance equal to one of said intervals during each said cycle, means forming images on the record medium in response to selective operation of said character generators during any of the cycles, and means for obtaining visible copies of said images after a number of cycles sufficient to have presented all characters in a station to each said interval of the particular length of the record medium.
 2. A page reproduction system as defined in claim 1, wherein said record member is a page blank.
 3. A page reproduction system as defined in claim 2, wherein said page blank comprises an insulating layer on a conductive backing.
 4. A page reproduction system as defined in claim 3, wherein said insulating layer is mounted on a paper treated with a conductive material.
 5. A page reproduction system as defined in claim 1, further including a resilient, conductive layer intermediate said supporting curved member and said record medium.
 6. A page reproduction system as defined in claim 5, wherein said record member is a page blank comprising an insulating layer on a conductive backing.
 7. A page reproduction system as defined in claim 6, wherein said insulating layer is mounted on a paper treated with a conductive material.
 8. A page reproduction system as defined in claim 1, wherein said character generators comprise opaque symbols in columnar arrangement on the transparent surface of a first cylindrical drum, said curved member is a second cylindrical drum having as said record medium a photoconductive element on the periphery thereof and being axially spaced from said first drum, said means forming images comprise a source of electrostatic charges for forming a uniform charge layer on the photoconductive element and a plurality of light sources, each cooperating with a respective column of said symbols and selectively operable to illuminate desired ones of said symbols, including blanks, in each said column, and said means for forming visible images include toning and transfer means.
 9. A page reproduction system as defined in claim 1, further including a high voltage source, and whErein said plurality of reproduction stations comprises font wheels fixed to a common axis for simultaneous rotation, each font wheel being separately energizable by said high voltage source at selected intervals in said rotation.
 10. A page reproduction system as defined in claim 9, wherein said record member is a page blank.
 11. A page reproduction system as defined in claim 10, wherein said page blank comprises an insulating layer on a conductive backing.
 12. A page reproduction system as defined in claim 11, wherein said insulating layer is mounted on a paper treated with a conductive material.
 13. A page reproduction system as defined in claim 9, further including a resilient, conductive layer intermediate said supporting curved member and said record medium.
 14. A page reproduction system as defined in claim 13, wherein said record member is a page blank comprising an insulating layer on a conductive backing.
 15. A page reproduction system as defined in claim 14, wherein said insulating layer is mounted on a paper treated with a conductive material.
 16. A page reproduction system as defined in claim 9, wherein said curved member is a cylindrical drum having as said record medium a dielectric material on the surface thereof and being axially spaced from said common axis sufficient to maintain a slight gap between said drum and said font wheels, and said means for forming visible copies of the images comprise paper sheets fed past said drum.
 17. A page reproduction system as defined in claim 16, wherein charge images formed on said drum are transferred to said paper sheet and further including means for toning said imaged paper and means for fixing the toned image on said paper.
 18. A page reproduction system as defined in claim 16, further including means for toning the images formed on the drum, means transferring toned images from the drum to said paper sheets, and means for fixing the toned image transferred to said paper. 